LSI offers a family of MegaRAID battery backup units for use with our high-performance MegaRAID storage adapters. These backup units protect the integrity of the cached data by providing power if there is a server failure or complete AC power failure. The industry-exclusive MegaRAID transportable battery backup units (TBBUs) offer an additional layer of fault tolerance by protecting data in cache during adapter field replacement.

MegaRAID Battery Backup Units (BBU) BAT-NIMH-3.6-03
Add-on modules that protect against data loss in the event of a power failure or server failure by providing emergency power to the cache memory. When power is restored, the data not yet written to the hard drives can be retrieved from cache memory.